Lawn Overseeding Calculator
Calculate the seed rate for overseeding an existing lawn and the best timing.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Estimate seed and cost for overseeding using fixed rates for the listed cool-season grasses and a lawn-thinning factor. Results do not account for cultivar or local climate; use the seed label and local extension guidance for timing and rate.
Worked example
calculated with the default values below
Lawn area 5,000 sq ft · Grass type Tall fescue (3 lb/1000 sq ft) · How thin is the lawn Moderate (1×) · Price per pound of seed 4 $ Seed needed 15.00 lb · 5 lb bags needed 3 · Seed cost 60.00 $
General background references
Disclaimer
These are general gardening estimates. Planting windows, growth, water and nutrient needs vary by place and plant. Check local extension guidance and product labels before acting on an estimate.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
seed_lb=A÷1000×r×T; bags=ceil(seed_lb÷5); cost=seed_lb×price
- A
- lawn area (sq ft)
- r
- fixed cool-season grass rate (lb/1,000 sq ft)
- T
- thinning factor
- price
- entered price per lb
Grass rates and thinning multipliers are model assumptions. Timing and actual rate depend on cultivar, climate and the seed label; the calculator does not predict composting or germination time.
Frequently asked questions
Are the seed rates a product recommendation?
No. The listed grass rates and thinning multipliers are planning assumptions. Actual rates and timing depend on cultivar, climate, lawn condition and the seed label; follow the product directions and local extension guidance.